1. Field of the Invention
The present invention relates to a liquid discharge head capable of discharging liquid, and more particularly to an inkjet recording head configured to discharge ink droplets onto a recording medium to perform a recording operation. Furthermore, the present invention relates to a method for manufacturing the liquid discharge head.
2. Description of the Related Art
A general inkjet recording head is equipped with discharge energy generating elements to discharge ink droplets. The discharge energy generating element is constructed from, for example, a heater or other electrothermal transducer, or a piezoelectric element or other piezoelectric type device. The discharge amount of an ink droplet can be controlled based on an electric signal supplied to the discharge energy generating element.
The demand for high resolution recording images has rapidly increased due to widespread use of the Internet and digital cameras. To realize such high resolution recording images, the inkjet recording heads are required to have smaller-size discharge ports capable of discharging fine ink droplets.
However, if the discharge port has a smaller diameter in the level of several μm, the flow resistance of liquid flowing in the discharge portion is extremely high. so that the discharge efficiency deteriorates.
To solve this problem, a conventional inkjet recording head discussed in U.S. Pat. No. 6,984,026 includes a first discharge portion including a discharge port and a second discharge portion having a larger cross section perpendicular to the flow direction compared to the discharge port.
The proposed conventional inkjet recording head can reduce the flow resistance of the fluid flowing toward the discharge port and accordingly can improve the discharge efficiency.
However, in the discharge test conducted based on samples of the head discussed in U.S. Pat. No. 6,984,026, the inventors of the present invention have confirmed some samples undesirable in discharge characteristics (e.g., in the discharge direction or in the discharge amount), in rare cases, depending on the shape (e.g., the size of discharge port diameter) or the material.
In the test, the inventors of the present invention have checked the head samples having undesirable discharge characteristics and found deformation, at least partly, in the vicinity of a member surrounding the discharge port.
Furthermore, as a result of study and analysis, the inventors of the present invention have confirmed the distortion caused by stress acting on the member surrounding the discharge port.
More specifically, a channel forming member of the inkjet recording head is directly brought into contact with the ink for a long time. Therefore, the channel forming member may cause swelling or thermal expansion depending on the material. The generated stress tends to cause deformation of the discharge portion because the discharge portion is thin and weak compared to other portion.